(1) Field of the Invention
The invention relates to a method of diagnosing nutrition of crop by obtaining crop information represented by nitrogen content, etc. of the crop from reflection light of the crop growing in a field. The invention also relates to a method of compensating the amount of reflection light obtained individually by a plurality of image elements.
(2) Description of the Related Art
A first conventional method for obtaining crop information such as a nitrogen content rate of a crop, a leaf color value, a nitrogen absorption amount, a plant height, a dry matter weight, etc., is one in which the amount of reflection light from the reference plate and the crop in the field is obtained by image-taking, by a light receiving means such as a digital camera, the reference plate which is coated with barium sulfate, etc. and the unit field (or a part of it) in which the crop grows, the reflectance of the crop is obtained from the amount of the light reflected from the reference plate and the crop, and the nitrogen content rate (amount of nitrogen absorption, a value of leaf color, a plant height, a dry matter weight) is obtained from the reflectance obtained and the relation formula predetermined for obtaining the nitrogen content rate (amount of nitrogen absorption, a value of leaf color, a plant height, a dry matter weight) from the reflectance, and the growth diagnosis has been conducted by comparing with a standard nitrogen content rate of that time period based on the number of growth days versus the nitrogen amount curve. However, the amount of reflection light of the crop to be obtained from the field is subject to change by weather. Also, even when the weather is compensated by the reference plate, it is necessary that each of the measuring direction, wind, and planting density be in the same condition as that applied when the predetermined relation formula was prepared for obtaining the nitrogen content rate from the reflectance. When the condition is different, the compensation is necessary accordingly, so that it cannot be said that all has been compensated only by obtaining the reflectance by the reference plate as reference. Actually, the measurement has been conducted under the limitation by the solar height, measuring direction, planting density or kind.
As for a second conventional method for obtaining crop information, there is an apparatus in which the light with a wavelength having relation to the crop information subject to increase or decrease depending on the growth of the crop, for example, the light ranging from a visible light region to a near infrared region is irradiated on a leaf blade of the crop and, based on the amount of the received light obtained with respect to the light with the wavelength having relation to the crop information and on the nitrogen amount related formula predetermined for calculating from the amount of light received, for example, a leaf blade nitrogen content, the leaf blade nitrogen content is measured. This apparatus is used to measure a number of leaf blades of the crop in the field and has enabled to obtain the leaf blade nitrogen content with a high precision. However, in order to grasp the crop information accurately for the overall field, a minute measurement extending to the overall field was indispensable, which is complicated and troublesome.
In the case where, as in the nutrition diagnosis of the crop leaf conducted according to the first conventional method, the so-called xe2x80x9cremote sensingxe2x80x9d is conducted and a comparatively large extent of field is subjected, the observation is made from quite far away so that there has occurred no large difference in areas of object corresponding to one image element of the camera. Therefore, there has occurred no difference in respective image elements in the resolution of the camera, either. On the other hand, in the xe2x80x9cremote sensingxe2x80x9d conducted quite close to the object, there occurs no large difference in areas of the object corresponding to one image element so that the measurement can be made in similar degree as above.
The first method described above is one in which, although the measurement is simple, the crop information to be obtained from the field is influenced by factors such as a measuring location and a planting density and, because of constraint in the measuring time and location, the method cannot be regarded as accurate. Also, when the camera is directed to the field and takes an image, the amount of reflection light obtained in each image-taking element of the camera has required compensation by a depression angle or field angle with respect to the field or a location such as this side or an opposite side in a large field. The distance between the camera and the field as the object varies for each image element, and the image-taking area obtained for each image element varies for respective distances. Further, the reflection angle differs by the depression angle and has an influence to the amount of reflection light. The second method, having no restraint in the measurement and having a high precision, is more advantageous than the first method. However, the problems in the second method are that the measurement has to be made for each leaf blade, thus requiring a large number of points to be measured and a long time accordingly.
The conventional remote sensing is conducted under the restrained condition that no large difference occurs in the area of the object for each image element. This is done for the reason of facilitating the subsequent compensation. However, because of the above restraint, a large scale observation means is required in order to enable taking an image of a large area and, if an image is taken extremely closely, the area of measurement becomes very small and it necessitates the measurements a plurality of times.
An object of the present invention is that, when obtaining the crop information by measuring the amount of reflection light, even though the camera is placed on the ground, compensation can be made so that no large error occurs, and a method of diagnosing nutrition of the crop provided is simple in the measurement of the crop information and enhances the measurement precision.
As a first method according to the present invention, the method of diagnosing nutrition of a crop in a field is arranged wherein: a camera equipped with a plurality of image elements is located in a predetermined central depression angle with respect to a field; an amount of reflection light of a crop leaf is obtained for each image element by image-taking the field; an image-taken area is obtained for each unit image element by an area function constituted by a conversion variable including a ground clearance of the camera, an image element depression angle, the number of image elements and a field angle; an area compensation is made of the amount of reflection light for each image element; a depression angle compensation is made of the amount of reflection light by the depression angle coefficient predetermined for compensating differences of amounts of reflection light correspondingly with image element depression angles; an amount of light incident on the crop leaf is measured; reflectance is obtained from the amount of the reflection light compensated and the measured amount of incident light; and crop information in a predetermined area based on the reflectance and a first crop related formula predetermined for obtaining the crop information is obtained and made first crop information. The first crop information is stored. By irradiating crop in the same area, an amount of at least either of transmission light or reflection light which is subject to increase and decrease depending on growth of the crop and which has a wavelength having relation to the crop information is measured, and crop information from the amount of light and a second crop related formula predetermined from the amount of light for obtaining crop information is obtained and stored as second crop information. The nutritious condition of the crop in the field is determined based on the first and second crop information.
The obtaining of the first crop related formula determined by obtaining the reflectance obtained from the amount of reflection light of the crop and the amount of reflection light for obtaining the first crop information in advance has been subject of research and is conventional. Also, the obtaining of the second crop related formula for obtaining the second crop information determined by obtaining the reflectance by irradiating the light on leaves has been subject of research and is conventional. Therefore, it is easy to obtain them individually. The present invention provides the method of diagnosing nutrition of the crop in which, for obtaining the first crop information, the difference in the amount of light caused by the difference in the light receiving area for each image element location of the camera having different image-taking ranges between the image element image-taken near by and the image element image-taken far away is compensated based on the image-taking angle between the so-called digital camera having a plurality of image elements provided in the field or based on, for example, the depression angle corresponding to the ground clearance of the camera which naturally occurs or on the field angle caused by the structure of the camera.
For the differences in the image-taking areas with respect to the amounts of light obtained for each unit image element, the specific (area) function for obtaining the area image-taken for each image element is determined by the secondary projection conversion by using the ground clearance of the camera and the accompanying depression angle for each image element, and the inherent coefficients of the camera such as the number of image elements which depends on the structure of the camera, the size of the image-taking elements which are aggregation of the image elements, and the angle of field which depends on the converging lens. Therefore, when the image-taken area for each image element is calculated by using the ground clearance and the depression angle as variables, or by adding the coefficients inherent to the camera as variables, and the amount of reflection light for each image element is divided by the image-taking area for each image element, it is possible to obtain the amount of reflection light for each image element which is not influenced by the image-taking area. In this way, the compensation relating to the distance between the camera and the image-taking location (this side or the opposite side) is realized.
Further, since there are a plurality of image elements, the depression angle is different for each unit image element. Thus, first, the image element in which the reference depression angle becomes, for example, 60xc2x0, and the compensation (depression angle) coefficient is made, for example, xe2x80x9c1xe2x80x9d is decided in advance. Then, while the depression angle is being varied, the reflection light amount at the same location of the crop field is measured for each depression angle and, from the varied amount of the reflection light amount based on the varied depression angle, it is possible to obtain the compensation coefficient at each depression angle. Based on the compensation coefficient, that is, the depression angle coefficient, obtained as above and the reflection light amount of each unit image element, the reflection light amount of each image element is compensated. In this way, it is possible to realize the compensation concerning the depression angles which vary by locations of the image elements.
At the depression angle which has been used as reference for the depression angle compensation in the above, the light amount of the natural light, that is, the light amount incident on the crop leaf may be calculated from the reflection light amount obtained by the reference reflection plate, and the reflectance of the image element can be calculated based on the amount of the natural light obtained as above and on the reflection light amount of the crop leaf obtained from the same image element. Similarly, by obtaining the reflection light amount for each image element, the reflectance of each unit image element can be obtained from the ratio with respect to the amount of the natural light. Further, it is also possible to calculate the reflectance from the ratio of the reflection light amount of the reference reflection plate and the reflection light amount of the unit image element.
The reflectance of the unit image element obtained as above is the reflectance of the unit image element obtained by the image-taking of the crop field by the camera on the ground, and is the reflectance in which any influence from the height or depression angle of the camera with respect to the crop field or from the structure of the camera has been compensated. Based on this reflectance and the reflectance of the crop leaves whose crop information is known, the first crop related formula determined in advance for obtaining the crop information from the reflectance is obtained by multiple regression analysis, and from the first crop related formula and the reflectance obtained by the compensation and the calculation explained above, it is possible to obtain the first crop information of the crop leaves. The wavelength of the amount of reflection light is not limited to 1, and the amount of reflection light at a wavelength necessary for obtaining the crop information is measured. Therefore, a task is necessary to obtain the reflectance for each of a plurality of wavelengths. For calculating respective functions or coefficients, it is possible to combine amounts of reflection light at a plurality of wavelengths.
In the method for obtaining the second crop information, the light which has a wave length having relation to the crop information subject to increase or decrease depending on the growth of the crop, for example, the light ranging from a visible light region to a near infrared region is irradiated directly on a leaf blade of the crop and, based on at least the reflection light amount or the transmission light amount obtained with respect to the light which has the wavelength having relation to the crop information and on the nitrogen amount related formula predetermined for calculating the leaf blade nitrogen content from the amount of light received by the crop leaves whose crop information, for example, a leaf blade nitrogen content is known, the leaf blade nitrogen content can be measured. This is embodied in an apparatus and is used to measure many leaf blades of the crop in the field and has enabled to obtain the leaf blade nitrogen content with a high precision. Thus, the method is useful in making a further compensation in the first crop information described above.
As a second method according to the present invention, the method of diagnosing nutrition of a crop in a field is arranged wherein: a camera equipped with a plurality of image elements is located in a predetermined central depression angle with respect to the field; an amount of reflection light of a crop leaf is obtained for each image element by image-taking the field; an image-taken area is obtained for each unit image element by an area function constituted by a conversion variable including a distance of field of view of the camera, an image element depression angle, the number of image elements and a field angle; an area compensation is made of the amount of reflection light for each image element; an image element depression angle compensation is made for the amount of reflection light by an image element depression angle coefficient predetermined for compensating differences in the amounts of reflection light according to the image element depression angles; an amount of light incident on the crop leaf is measured, reflectance is obtained from the amount of reflection light compensated and the above measured amount of light; and crop information in a predetermined area based on the reflectance and a first crop related formula predetermined for obtaining the crop information is obtained and made a first crop information. The method further comprises storing the first crop information, irradiating light on a leaf blade of the crop in the same area, measuring the amount of at least one of the transmission light and the reflection light which is subject to increase and decrease depending on growth of the crop and which has a wavelength having relation to the crop information is measured, obtaining crop information based on the amount of light and on a second crop related formula predetermined for obtaining the crop information from the amount of light and storing the crop information as second crop information, and diagnosing nutrition of the crop from the first crop information and the second crop information.
In this second method, in stead of the depression angle utilized for the specific function in the first method described above, the field distance of the camera is used. The specific (area) function for obtaining the area image-taken for each image element is determined by the secondary projection conversion by using the ground clearance of the camera and the accompanying depression angle for each image element, and the inherent functions of the camera such as the number of the image elements which depends on the structure of the camera, and the functions inherent to the camera such as the number of image elements which depends on the structure of the camera, the magnitude of the image-taking elements which are aggregation of the image elements, and the field angle which depends on the converging lens. Therefore, when the image-taken area for each image element is calculated by using the ground clearance of the camera and the field distance as variables, or by adding the coefficient inherent to the camera as variables, and the amount of reflection light for each image element is divided by the image-taking area for each image element, it is possible to obtain the amount of reflection light for each image element which is not influenced by the image-taking area. In this way, the compensation relating to the distance between the camera and the image-taking location (this side or the opposite side) is realized. With reference to the first crop information and the second crop information, how they are obtained has already been explained so that the explanation is not repeated here.
In the first and the second nutrition diagnosing methods explained above and the crop diagnosis to which such methods are applied, the first crop information may be obtained for each unit crop field, or may be obtained for each unit area which is arbitrary determined and which is smaller than the unit crop field. The unit crop field here refers to one field divided by what is normally called xe2x80x9cfurrowxe2x80x9d.
As a third method according to the present invention, the method of diagnosing nutrition of a crop in a field is arranged wherein: a camera equipped with a plurality of image elements is located in a predetermined central depression angle with respect to a field; an amount of reflection light of a crop leaf is obtained for each image element by image-taking the field; an image-taken area is obtained for each unit image element by an area function constituted by a conversion variable including a ground clearance, an image element depression angle, the number of image elements and a field angle; an area compensation is made of the amount of reflection light for each image element; a plurality of image elements are divided into sections based on the image-taken area of the unit image element corresponding to the maximum area among the image-taken areas obtained for each unit image element; reflectance is obtained from the amount of reflection light for each section and the amount of light incident on the crop leaf; and crop information in a predetermined area based on said reflectance and a first crop related formula predetermined for obtaining the crop information is obtained and made the first crop information, and nutrition of the crop is diagnosed from said first crop information.
The present invention provides the method of diagnosing nutrition of the crop in which, for obtaining the first crop information, the difference in the amount of light caused by the difference in the light receiving area for each image element location of the camera having different image-taking ranges between the image element image-taken near by and the image element image-taken far away is compensated based on the image-taking angle between the so-called digital camera having a plurality of image elements provided in the field or based on, for example, the depression angle corresponding to the ground clearance of the camera which naturally occurs or on the field angle caused by the structure of the camera.
Since the way as to how the differences in the image-taking areas with respect to the amounts of light obtained for each unit image element is the same as in the first method explained above, no explanation is repeated here.
Further, according to the third method of the invention, a plurality of image elements are divided based on the image-taking area of the unit image element corresponding to the maximum area among the plurality of the image elements. When the camera is directed to the crop field, the crop field area which is obtained by one image element becomes larger as the camera is far from the crop field. Thus, the division is worked out by using the maximum area of the crop field area obtainable by one image element as reference and, for forming the same area, other image elements are combined. That is, even though the numbers of image elements are different, the crop field area divided is the area of constant size for obtaining the reflected light. In this case, the maximum area of the crop field area which can be obtained by one image element is made the reference. The amount of the reflection light can be obtained at the constant area so that, when the camera is placed on the ground, even when there are differences in the crop field areas obtained for respective image elements, they can be divided into the constant areas, thus enabling to obtain the amount of the reflection light which has no influence to the resolution by the camera.
On the other hand, according to the fourth method, the reflectance is sought, of the image-taken areas obtained for each of the unit image elements, from the amount of reflection light of the unit image element below the predetermined image-taken area and the amount of light incident on the crop leaf. When the camera is directed to the crop field, the field area obtainable by one image element becomes larger as the camera is further away. Therefore, the information from the image element image-taken of a field area exceeding the area predetermined as appropriate for the nutrition diagnosis of crop leaves is unaccepted, and only the information from the image element image-taken of a field area below the predetermined area is treated as acceptable. And, by using the predetermined area of the crop field obtained by one image element as reference, other image elements are combined so as to be the same divided area in size. That is, even though the number of image elements differs, the image elements are so divided as to form the predetermined same size area of the crop field for purposes of the amount of reflection light. The reference at this time is a predetermined crop field area. Since the amount of reflection light can be obtained with respect to the predetermined area, the camera may be placed on the ground, and the crop field areas obtained for respective image elements may differ, but the areas may be divided into the predetermined area. In this way, it is possible to obtain the amount of reflection light which has no influence to the resolution of the camera. The predetermined area here is meant for the crop field area which is appropriate for the nutrition diagnosis of the crop leaves, for example, in the order of 1 m2 to 5 m2.
By calculating the ratio between the amount of reflection light from the fixed area or the predetermined area obtained as explained above and the amount of reference reflection light of the reference plate or the amount of light incident on the crop leaf by solar light, the calculated ratio is made a reflectance for the fixed area or the predetermined area.
The reflectance of the fixed area or the predetermined area obtained as above is the reflectance obtained by the image-taking of the crop field by the camera on the ground, and is the reflectance in which any influence from the height or depression angle of the camera with respect to the crop field or from the structure of the camera has been compensated. Based on this reflectance and the reflectance of the crop leaves whose crop information is known, the first crop related formula determined in advance for obtaining the crop information from the reflectance is obtained by multiple regression analysis, and from the first crop related formula and the reflectance obtained by the compensation and the calculation explained above, it is possible to obtain the first crop information of the crop leaves. The wavelength of the amount of reflection light is not limited to 1, and the amount of reflection light at a wavelength necessary for obtaining the crop information is measured. Therefore, a task is necessary to obtain the reflectance for each of a plurality of wavelengths. For calculating respective functions or coefficients, it is possible to combine amounts of reflection light at a plurality of wavelengths.
As a fifth method according to the present invention, in the method of diagnosing nutrition of a crop in a field, a camera equipped with a plurality of image elements is located in a predetermined central depression angle with respect to a field; an amount of reflection light of a crop leaf is obtained for each image element by image-taking the field; an image-taken area is obtained for each unit image element by an area function constituted by conversion variables including a field distance of the camera, an image element depression angle, the number of image elements and a field angle; an area compensation is made of the amount of reflection light for each image element; a plurality of image elements are divided into sections based on the image-taken area of the unit image element corresponding to the maximum area among the image-taken areas obtained for each unit image element; reflectance is obtained from the amount of reflection light for each section and the amount of light incident on the crop leaf; and crop information in a predetermined area based on said reflectance and a first crop related formula predetermined for obtaining the crop information is obtained and made first crop information, and nutrition of the crop is diagnosed from said first crop information.
In this fifth method, in stead of the depression angle utilized for the specific function in the first method described above, the field distance of the camera is used. That is, with reference to the difference in the image-taking area with respect to the amounts of the light obtained for each image element, the specific (area) function for obtaining the area image-taken for each image element is determined by the secondary projection conversion by using the ground clearance of the camera and the accompanying field distance (distance between the image element and the image-taking point) for each image element, the number of the image elements and the inherent functions of the camera such as the number of image elements which are based on the structure of the camera and the magnitude of image-taking elements which are the aggregation of the image elements, and the field angle, etc. which is based on the converging lens. Therefore, when the image-taken area for each image element is calculated by using the ground clearance and the field distance of the camera as variables, or by adding the coefficient inherent to the camera as variables, and the amount of reflection light for each image element is divided by the image-taken area for each image element, it is possible to obtain the amount of reflection light for each image element which is not influenced by the image-taken area. In this way, the compensation relating to the distance between the camera and the image-taking location (this side or the opposite side) is realized. Among the image-taken areas of unit image elements, the maximum area is used as reference, and other image elements are divided for obtaining the fixed area in dimension. In this respect the explanation made in the third embodiment applies and the same explanation is not repeated here.
According to a sixth method of the invention, a method of diagnosing nutrition of crop in a field is arranged wherein: a camera equipped with a plurality of image elements is located in a predetermined central depression angle with respect to a field; an amount of reflection light of a crop leaf is obtained for each image element by image-taking the field; an image-taken area is obtained for each unit image element by an area function constituted by a conversion variable including a field distance of the camera, an image element depression angle, an image element number and a field angle; an area compensation is made of the amount of reflection light for each image element; reflectance is obtained from the amount of reflection light of the unit image element which becomes smaller than the predetermined image-taken area among the image-taken areas obtained for each unit image element and the amount of light incident on the crop leaf; and crop information in a predetermined area based on said reflectance and a first crop related formula predetermined for obtaining the crop information is obtained and made first crop information, and nutrition of the crop is diagnosed from said first crop information.
In the sixth method of the invention, in stead of the depression angle utilized for the specific function in the fourth method, the depression angle is used. For the differences in the image-taking area with respect to the amounts of light obtained for each image element, the specific (area) function for obtaining the area image-taken for each image element is determined by the secondary projection conversion by using the ground clearance of the camera and the accompanying depression angle for each image element, and the inherent functions of the camera such as the number of the image elements which depends on the structure of the camera, and the functions inherent to the camera such as the number of image elements which depends on the structure of the camera, the magnitude of the image-taking elements which are aggregation of the image elements, and the field angle which depends on the converging lens. Therefore, when the image-taken area for each image element is calculated by using the ground clearance and the depression angle as variables, or by adding the coefficient inherent to the camera as variables, and the amount of reflection light for each image element is divided by the image-taking area for each image element, it is possible to obtain the amount of reflection light for each image element which is not influenced by the image-taking area. In this way, the compensation relating to the distance between the camera and the image-taking location (this side or the opposite side) is realized. When the crop field area obtained is smaller than the predetermined area, the unit image elements are adopted, and the adopted image elements are divided for forming the predetermined area. The method of dividing is the same as that explained for the fourth method and the explanation is not repeated.
For obtaining the second crop information, the light which has a wave length having relation to the crop information subject to increase or decrease depending on the growth of the crop, for example, the light ranging from a visible light region to a near infrared region is directly irradiated on a leaf blade of the crop and, based on at least one of the amount of the reflection light and the amount of the transmission light obtained with respect to the light which has the wavelength having relation to the crop information and on the nitrogen amount related formula predetermined for calculating the amount of nitrogen content in the leaf blade from the amount of light in the crop leaf whose crop information, for example, the amount of nitrogen content in the leaf blade is known, the amount of nitrogen content in the leaf blade can be measured. This apparatus is used to measure many leaf blades of the crop in the field and is able to obtain the leaf blade nitrogen content with a high precision. Thus, it is effective to compensate further the first crop information described above.
An effective method for compensation by the combination of the two useful methods for obtaining the above explained first crop information and second crop information is explained hereunder. The difference between the first crop information and the second crop information obtained respectively is first calculated. By using this difference for compensating the first crop information, it is possible to compensate not only the errors caused by weather changes (weather, time, solar position) but also the errors caused by changes in cultivation factors (measuring direction, planting density) which have heretofore been considered difficult to be compensated. This method is especially suited for conducting nutrition diagnosis at a plurality of spots in the same field because the determination for the compensation is simple and easy.
Where the difference between the first crop information and the second crop information decided as above is stored, only by obtaining the first crop information from the unknown crop in the fixed area in the field from which the first crop information has been obtained, it is possible to compensate the first crop information by the first crop information and the above difference. This method enables the easy compensation of the errors caused by the planting density and the measuring direction, and the method may be embodied in an apparatus with the compensation value being provided. Such apparatus can be readily used for crop nutrition diagnosis.
For conducting a more strict compensation than in the first to fourth crop nutrition diagnosing methods, the following method is applied. That is, after the first crop information is obtained and divided into a plurality of divisions, at least two points of data from within the plurality of divisions are selected, and the second crop information is obtained directly from the crop leaves in the same field as the field from which the two points of data are selected. Thus, from the two points of data of the first and the second crop information, the correlation thereof is determined and the compensation conversion formula is defined and, based on this formula, all the values in the plurality of divisions are compensated. In obtaining the compensation conversion formula, the plurality of crop information can be obtained from the fixed extent of area and, further, from the compensation conversion formula, the first crop information can be compensated for a large extent of area.
For conducting a compensation in the first to fourth crop nutrition diagnosing methods, there is another method as follows. In the field exposed to natural light, the reflectance of the light that has wavelength having relation to the crop information subject to increase or decrease depending on the growth of crop is measured and, based on the reflectance and the first crop related formula predetermined for obtaining the crop information from the reflectance, the crop information for each division is obtained and stored. Then, from the first crop information stored in the respective divisions, the crop information in at least two divisions is selected, and the light is irradiated on the crop leaf blades from the two divisions of the field and the amount of at least transmission light or reflection light having relation to the crop information subject to increase and decrease depending on the growth of the crop is measured. Then, based on the amount of light and the second crop related formula predetermined for obtaining the crop information from the amount of light, the crop information from the two section is obtained and stored, and the compensation conversion formula for compensating the first crop information based on the second crop information is determined and is made third crop information after compensating the first crop information for each division by the compensation related formula. The third crop information thus obtained may be used for nutritious diagnosis of the crop in the field.
This method obtains the information relating to the plurality of divisions individually. The data of at least two divisions are selected from among the plurality of divisions and, by obtaining the second crop information directly from the crop leaves from the same divisions as the divisions from which data in the two divisions are obtained, the correlation between the first crop information and the second crop information is determined by the data of the two points and the compensation conversion formula is defined. Based on this formula, all the values of the plurality of divisions can be compensated. In obtaining the compensation conversion formula, the plurality of crop information can be obtained from a large extent of area and, further, from the compensation conversion formula, the first crop information can be compensated for a large extent of area.
In the diagnosing methods described above, the first crop related formula and the compensation conversion formula are stored and the reflectance from the crop leaves of unknown fields is measured whereby, based on the first crop related formula and the compensation conversion formula, the third crop information can be obtained. Where these items are stored in a memory section of a control means and are used for appropriate operation, the method can be realized as an apparatus which, not only realizes the diagnosing of the crop but also contributes in enhancing the precision in the measurement.
The arbitrary two divisions to be selected from among the plurality of divisions may be divisions of the maximum value and the minimum value, respectively, from the first crop information. In this way, the straight line in the compensation conversion of the first crop information and the second crop information can be determined readily at the two points, high and low, without being affected by the remaining data.
There can be various crop information but, for purposes of diagnosing nutrition of the crop, the nitrogen content of leaves or the color values of leaves are considered to be the best. This is understandable from the fact that, in the crop, the nitrogen content in leaves is the factor which immediately shows the effectiveness of the fertilization or whether the fertilization is appropriate or not.
In the above crop diagnosing methods, in order to measure the reflectance of the light which has wavelength having relation to the crop information subject to increase or decrease depending on the growth of the crop, the reflectance of the crop is image-taken by the image-taking elements constituted by a plurality of image elements, the image elements having received the reflection light corresponding to the crop are selected, and the reflectance is measured based on the light received data of the selected image element, thereby providing a method of diagnosing the crop by obtaining the first crop information. The reflection light obtained by an image-taking means such as a digital camera is influenced by the planting density or the dimension of the image-taken field, for example, whether the unit field is within the extent of 1 m2, so that the light image-taken of the crop as the reflection light is not necessarily the reflection light. That is, from the stand point of the unit image element, the reflection light from other than the crop, for example, the light reflected from the soil of the field may be included. Thus, it is desired that only the image elements which relate to the reflectance of the predetermined extent of area be selected and be used as the reflection light from the crop, and the first crop information be obtained based on such data of the received light.